Deterioration in resolution of a radar using long slotted waveguide antenna

The deterioration in resolution in a long slotted waveguide antenna is analyzed, and a way to minimize it is suggested. A long slotted waveguide antenna with a horizontal 3-dB beamwidth of 0.4 degrees , pulse length tau =40 ns, PRF f/sub o/=4 kHz, and f/sub c mod /=9.375 GHz is considered where the beam spreads from 0.4 degrees to 0.82 degrees with an interelement spacing of 0.52 lambda g. This beam spread decreases as the interelement spacing is increased. It is suggested that the beam spread can be reduced to some extent by increasing the interelement spacing with the constraint of not generating grating lobes. Therefore, using the largest possible separation between slots (without generating grating lobes), it is possible to reduce the deterioration in resolution (range and angular) in a long-slotted waveguide antenna.<>